The invention is related to a pressure cylinder and a method for adjusting the idle travel of a pressure cylinder being used, in particular, in hydraulic actuating systems in automotive vehicles. The invention relates to a pressure cylinder of the general type having an abutment face provided at a flange provided on a cylinder casing and which serves to fasten the pressure cylinder to a wall, and further including a piston positioned in a bore in the cylinder casing, which presents a pressure surface to receive a force applying member. Guided within a bore is a central valve with a tension element pretensioned by a captive spring arrangement. The tension element untensions as the piston moves and, under the effect of a spring arrangement which takes support through a support face provided at a spring retainer and a stop, the central valve interrupts a connection from a pressure chamber on one side of the piston to an intake chamber arranged behind the piston.
A pressure cylinder of this type described is in the German patent application No. (P 34 24 513.8). In order to reduce the idle travel of this pressure cylinder, compensation elements of different thickness are required to be positioned between the piston and the push-rod providing for the adjustment to a rated functional distance. This method, however, leads to increased assembly efforts and additional shims are needed. Also, the necessary thickness of the compensating elements can not be determined in a hydraulically full state of the pressure cylinder. That is, the pressure cylinder must be completely vented before the measuring operation. Only thereafter is it possible by sliding the push-rod piston to check the position at which the central valve closes. Such an adjusting procedure is comparatively complicated and expensive.
Pressure cylinders adjusted by the foregoing method which are filled with hydraulic fluid can not be stored over an extended period of time, since an alteration of the hydraulic fluid, such as, for example, the absorption of water from the air, may take place. This in turn may lead to corrosion damage at the pressure cylinder, jeopardizing later use of the pressure cylinders.